DESIGNED BY ELLA MARU STUDIO January 30, 2021 Chemical Bond Acts Like a Mash-Up January 30, 2021 Chemical Bond Acts Like a Mash-Up About this Guide In this Guide, based on the online Science News “This weird chemical bond acts like a mash-up of hydrogen and covalent bonds,” students will learn about recent research findings that challenge long- held ideas about chemical bonding and discuss how to incorporate exceptions to general chemistry concepts into their learning. This Guide includes: Article-based Comprehension Q&A — Students will answer questions about the online Science News article “This weird chemical bond acts like a mash-up of hydrogen and covalent bonds,” which explores new research that suggests chemical bonds exist on a continuum. A version of the story, “Chemical bond acts like a mash-up,” can be found in the January 30, 2021 issue of Science News. Related standards include NGSS-DCI: HS-PS1; HS-PS2; HS-PS3. Student Comprehension Worksheet — These questions are formatted so it’s easy to print them out as a worksheet. Cross-curricular Discussion Q&A — Students will discuss the classical definitions of chemical bonds and determine how to adjust those definitions based on new research. Then, students will talk about the best strategies for assessing general chemistry concepts and exceptions to those generalizations. Related standards include NGSS-DCI: HS-PS1; HS-PS2; HS-PS3. Student Discussion Worksheet — These questions are formatted so it’s easy to print them out as a worksheet. January 30, 2021 Chemical Bond Acts Like a Mash-Up Article-based Comprehension, Q&A Directions for teachers: Ask your students to read the online Science News article “This weird chemical bond acts like a mash-up of hydrogen and covalent bonds,” which explores a new type of chemical bond, and answer the following questions. A version of the story, “Chemical bond acts like a mash-up,” can be found in the January 30, 2021 issue of Science News. 1. Define hydrogen bonds and covalent bonds based on the information provided in the Science News article. Of the two types of bonds, which is not considered a “true chemical bond?” Hydrogen bonds result from weak attractions between atoms in one molecule to oppositely charged atoms in a neighboring molecule. Covalent bonds result from electrons being shared among atoms, typically within a molecule. Unlike the covalent bond, the hydrogen bond is not considered a true chemical bond. 2. What is the new type of bond that scientists discovered? What makes it special? Researchers discovered what’s called a hydrogen-mediated chemical bond. At first it was thought to be an unusually strong variety of hydrogen bond. But experiments revealed that the bond is a hybrid of a hydrogen bond and a covalent bond, as it involves shared electrons—a characteristic of covalent bonds. 3. Where was the new bond found? Name and describe the molecule that contains the new bond. The new bond was found in bifluoride ions in water. A bifluoride ion consists of a hydrogen atom sandwiched between two fluorine atoms. 4. According to the rules of chemistry, how should the molecule have been bound together? How was the molecule actually bound together? According to the rules of chemistry, the hydrogen atom in one bifluoride molecule should be loosely bound to one fluorine atom via hydrogen bonding and closely bound to the other fluorine atom via covalent bonding. Instead, the hydrogen atom was shared equally between the fluorine atoms. 5. What did computer simulations reveal about the new bond’s behavior? As the fluorine atoms moved closer together and squeezed the hydrogen atom, the normal hydrogen bond became stronger until all three atoms began sharing electrons as in a covalent bond. 6. What does chemist Bogdan Dereka say about the discovery? The hydrogen-mediated bond erases the difference between covalent and hydrogen bonds so that the distinction is no longer meaningful. 7. Why is understanding strong hydrogen bonds important? Strong hydrogen bonds are thought to play a role in transporting hydrogen ions, a process crucial for powering living cells and for technologies such as fuel cells. Better understanding these bonds could shed light on a variety of effects. 8. What are the big-picture implications of the discovery? The discovery has implications for scientists’ fundamental understanding of what a chemical bond is, as well as what qualifies as a molecule. January 30, 2021 Chemical Bond Acts Like a Mash-Up Student Comprehension Worksheet Directions: Read the online Science News article “This weird chemical bond acts like a mash-up of hydrogen and covalent bonds,” which explores a new type of chemical bond. A version of the story, “Chemical bond acts like a mash-up,” can be found in the January 30, 2021 issue of Science News. 1. Define hydrogen bonds and covalent bonds based on the information provided in the Science News article. Of the two types of bonds, which is not considered a “true chemical bond?” 2. What is the new type of bond that scientists discovered? What makes it special? 3. Where was the new bond found? Name and describe the molecule that contains the new bond. 4. According to the rules of chemistry, how should the molecule have been bound together? How was the molecule actually bound together? 5. What did computer simulations reveal about the new bond’s behavior? 6. What does chemist Bogdan Dereka say about the discovery? 7. Why is understanding strong hydrogen bonds important? 8. What are the big-picture implications of the discovery? January 30, 2021 Chemical Bond Acts Like a Mash-Up Cross-curricular Discussion, Q&A Directions for teachers: Use the online Science News article “This weird chemical bond acts like a mash-up of hydrogen and covalent bonds” and the prompts below to have students explore classical definitions of chemical bonding and how those definitions should be revised based on new research. A version of the story, “Chemical bond acts like a mash-up,” appears in the January 30, 2021 issue of Science News. As a final exercise, have students discuss how to best learn general chemistry concepts and their exceptions. Want to make it a virtual lesson? Post the online Science News article “This weird chemical bond acts like a mash-up of hydrogen and covalent bonds,” to your learning management system. Pair up students and allow them to connect via virtual breakout rooms in a video conference, over the phone, in a shared document or using another chat system. Have each pair post its answers to the third set of questions, or conduct a class discussion to allow groups to share out. Classical definitions Discuss the following questions with a partner before reading the Science News article. Reference an outside resource if needed, but try to determine examples on your own. 1. What does electrostatic attraction mean? How does this concept apply to atoms and chemical bonding? Electrostatic attraction is the electric force between two oppositely charged bodies. The force of attraction between positively charged protons and negatively charged electrons within an atom, and the attractive forces between partially or fully charged molecules in a substance, impacts the chemical reactivity of the substance. 2. What is the difference between intermolecular and intramolecular attraction forces? Explain and give an example of each based on your understanding of the concepts. Intermolecular attraction forces are attractive forces between molecules. Intramolecular attraction forces are the attractive forces between atoms within a molecule. Generally, hydrogen bonds and dipole-diploe interactions are considered intermolecular attraction forces. Covalent bonds, both polar and nonpolar, are typically defined as intramolecular attractions. Ionic bonds are also generally thought of intramolecular forces. They are forces of attraction between charged atoms and/or molecules. Water, or H2O, can be used as an example of both intra-and intermolecular attraction forces. Hydrogen bonds occur between molecules of H2O, but within one H2O molecule, each hydrogen atom forms a polar covalent bond with the lone oxygen atom in the molecule. 3. What type of attraction force is generally thought of as a “true chemical bond?” What does this tell you about the general difference in attractive strength of intermolecular versus intramolecular attraction forces? Intramolecular attraction forces are generally viewed as true chemical bonds. These forces are very strong, meaning a lot of energy is generally required to separate atoms within molecules. Intermolecular attraction forces are generally less strong, meaning it doesn’t take much energy to separate molecules. 4. Why do we attempt to classify types of chemical bonds and/or attractive forces within a substance or mixture? To predict the physical and chemical properties of a substance, such as the ability to transport hydrogen ions, as mentioned in the Science News article. Modifying definitions Read the online Science News article “This weird chemical bond acts like a mash-up of hydrogen and covalent bonds,” and answer the following questions individually, before discussing them with a partner. 1. What is a hydrogen-mediated chemical bond and why is it unique? A hydrogen-mediated chemical bond is a hybrid of a hydrogen bond and a covalent bond. It is stronger than a typical hydrogen bond and involves electron sharing, which is typically characteristic of covalent bonding. 2. Given the information in the article, what chemistry terms need to be redefined? Why? Molecules and chemical bonds. The newly discovered hydrogen-mediated chemical bond does not fit into the conventional bond categories. It also redefines the conventional knowledge about what constitutes a molecule. Exceptions to the rules Discuss the following questions with a classmate. Write down your thoughts and be prepared to share your answers with the class.